Approach Lit Signal Aspects

Not sure if this belongs here or in the CSX thread, but here goes.

In Belleview, FL there is an approach lit signal that I pass almost every night in my job as a delivery driver; the road I'm on parallels the railroad for a while, so I can't miss the S/B display of it. I can normally tell if a train is coming when it displays green over red, however, last night I noticed it displayed yellow over yellow for a time, which I had never seen before.

I stopped to make a delivery, and noticed that the signal had then gone dark and no train ever appeared. Questions: Are routes sometimes set up by distant controllers (Jacksonville, in this case), and then cancelled out? What exactly does yellow over yellow mean as opposed to green over red? Thanks.

On your first question, yes. The dispatchers who are remotely controlling the signals can line up a route and then cancel it out (maybe they are just running tests...maybe they lined the wrong route...etc). HOWEVER, the dispatcher has no control over the approach lighting of the signal. An approach-lit signal is just that, lit by the approach of the train. So the signal going dark doesn't mean that the route was canceled. Just that there is no approaching train. For example, the dispatcher could send a train through an interlocking eastbound. As the train is leaving eastbound, it will occupy the approach of the westbound signals, lighting them (they would be at stop and display Red/Red). Knowing that the next train will be westbound, the dispatcher could request the westbound signal ahead of time. If you were looking out the back of the leaving eastbound train, you would see the signal behind the train go from Red/Red to Green/Red. Once the leaving train got a certain distance away, the signal would go dark. Internally, the signal is still cleared and displaying Green/Red, but the light bulbs themselves are turned off. Sometime later the second train comes allong moving westbound. When it gets a certain distance from the signal, the light bulbs are turned on again and the signal displays Green/Red.

On your second questions: The exact meaning of the signal depends on they type of signal, the railroad and the rules that they follow. With NORAC signal rules, Yellow/Yellow would mean Aproach Slow (be at slow-speed when you reach the next signal). With Seaboard signal aspects (which I think the CSX signal you are refering to would be) Yellow/Yellow would mean Advance Approach (be ready to stop two signals from now). Green/Red is pretty much universally a Clear (go your maximum authorized speed).

Many railroads have their signals programmed to go dark when there is no train in the approaching block. So once a train passes that signal it would go dark. If a train was coming the other way you'd see that the signal would be dark until the front of the train gets on the side facing the signal, at which time the signal would light up. This is common practice to save on bulbs.